The present application relates generally to the heat generated by a turbomachine; and more particularly to, a system and method for removing the heat remaining within a gas turbine and a combustion process has ended.
As a gas turbine operates, a combustion process heats various components. When the combustion process ends, these hot components heat the fluids remaining inside the gas turbine. Within the casing, the heated fluids have a density that is less than fluids at a lower temperature. The hotter fluids rise and cause a temperature gradient that leads to an upper casing at a higher temperature than a lower casing; and a hotter rotor at a 12:00 position than at a 6:00 position. This behavior can cause both the rotor and the casing to bow; possibility reducing the clearances between these components, which are formed of different materials.
There may be a few issues with the currently known systems and methods that address these issues. One solution slowly rotates the rotor. This process may yield relatively uniform temperatures at the 12:00 and 6:00 positions. However, this solution does not reduce bowing in the casing.
Another solution rotates the rotor at a faster speed, such as a crank speed, purge speed, or the like. This process forces cooling air across the rotor and the casing. This operation consumes a considerable amount of energy to spin the rotor and to maintain adequate lubrication of the rotor, bearings and other related components.
Another solution uses an external valve located on the upper casing. Here, an external air supply is forced into the casing via the external valve, as the rotor is rotated. This solution forces cooler air, at a high velocity, in a manner that impinges the hot components. This may cause increased thermal stress on those components.
For the foregoing reasons, there is a desire for a method and system that removes the heated fluid from the internal flow paths of a gas turbine. The system should not use a valve to force air into the internal flow paths, in a manner that causes the high velocity impingement.